This invention relates generally to a power adjuster system for seats of motor vehicles, and more particularly to a mechanism within such a system that prevents forces applied to the seat in a vehicle collision from being restrained entirely by the drive motor of the system.
Automotive power driven seat mechanisms are well known in the art. A typical power adjuster seat mechanism uses a worm gear driven by a motor connected to a rack and pinion to produce fore-and-aft movement of the seat. The typical current design of these systems relies on the geometry and internal friction of the gear drive to maintain the seat set in a desired position when it is not being moved.
The requirements of these products presents two conflicting design constraints. First, in order to keep an external load on the seat, such as that encountered in a vehicle collision, from moving the seat by xe2x80x9cback drivingxe2x80x9d the worm gear and drive motor, it has been necessary to use a relatively high gear reduction ratio. The high reduction ratio provides a high degree of friction. However, using a high gear ratio causes the rate of powered movement of the seta to be limited. Decreasing the gear tends to increase the speed with which the powered seat is capable of moving, but it also results in undesirable movement of the seat upon application of external forces to the seat. These concerns are especially significant with so-called integrated structural seats, which have belt restraint anchorages on the seat structure, and therefore, the seat which is movable on its tracks absorbs all restraint loadings. In short, past designs have had to sacrifice adjustment speed for rigidity and vice versa. Therefore, there is a need in the automotive industry for a seat power adjuster system that is rigid enough to withstand the application of high external forces, yet is capable of moving the seat relatively rapidly.
In accordance with the present invention, a power adjuster system is provided with an internal non-reversing clutch mechanism. The clutch mechanism is integrated into the power adjuster dear drive train. When the clutch is driven by the motor actuator to adjust seat position in either the fore or the aft directions, the clutch mechanism allows free rotation and driving engagement with the seat. If however, a high level of external force is acting on the seat, the clutch mechanism locks, transferring these loads directly to the seat track or other mounting structural member. Since the clutch is located between the seat and the drive motor actuator, locking of the clutch transfers forces away from the motor actuator. Since the motor drive system does not have to be designed with sufficient friction to withstand inertial or other external loads applied to the seat, that system can be optimized for its function of allowing position changes for the seat.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.